For the purpose of developing high performance hydrodesulfurization catalyst, increased numbers of work, based on precise analysis of catalyst active site structure using model support technique, have been carried out. Among those, we introduce following very attractive works. i.e. structural analysis of MoS2 clusters in atomic level by SPM, precise analysis of sulfidation mechanism by XPS, and study of the effect of support on the orientation of MoS2 clusters by HRTEM. New high performance catalysts are expected to be developed thorough these approach of surface science.